title: Triiodothyronine rapidly alters the TSH content and the secretory granules distribution in male rat thyrotrophs by a cytoskeleton rearrangement-independent mechanism.
abstract: Rapid actions of T3 on TSH synthesis in posttranscriptional steps, such as polyadenylation and translation rate, have already been described. The focus of this paper was to characterize rapid actions of T3 on TSH secretion and the involvement of actin and microtubule cytoskeleton in this process. For that, sham-operated (SO) and thyroidectomized (Tx) rats were subjected to acute or chronic treatment with T3. We observed a disarrangement in microtubule and actin cytoskeletons and an increase in Tshb mRNA levels in Tx rats, whereas the total TSH protein content was reduced in the pituitary gland as a whole, but increased in the secretory granules close to the plasma membrane of thyrotrophs, as well as in the extracellular space. The acute T3 dose promoted a rapid increase and redistribution of TSH secretory granules throughout the cytoplasm, as well as a rearrangement in actin and microtubule cytoskeletons. The T3 chronic treatment outcome reinforces the acute effects observed and, additionally, evinces an increase in the α-tubulin content and a rearrangement in microtubule cytoskeleton. Thus, T3 is able to rapidly suppress TSH secretion and, in parallel, to promote a rearrangement in actin and microtubules assembly throughout the pituitary gland, effects that seem to be independent from each other.
authors.affiliation: PhD, Full Professor, Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Avenue Professor Lineu Prestes, 1524, CEP 05508-000, Sao Paulo, Brazil. mtnunes@icb.usp.br.
authors.forename: Paula
authors.initials: P
authors.lastname: Bargi-Souza
authors.forename: Renata Marino
authors.initials: RM
authors.lastname: Romano
authors.forename: Renato de Mayrinck
authors.initials: Rde M
authors.lastname: Salgado
authors.forename: Francemilson
authors.initials: F
authors.lastname: Goulart-Silva
authors.forename: Erika Lia
authors.initials: EL
authors.lastname: Brunetto
authors.forename: Telma Maria Tenório
authors.initials: TM
authors.lastname: Zorn
authors.forename: Maria Tereza
authors.initials: MT
authors.lastname: Nunes
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D003599:Cytoskeleton / Q000502:physiology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D022142:Secretory Vesicles / Q000502:physiology*; D013965:Thyroidectomy; D052684:Thyrotrophs / Q000166:cytology* / Q000378:metabolism; D013972:Thyrotropin / Q000378:metabolism*; D037322:Thyrotropin, beta Subunit / Q000235:genetics / Q000378:metabolism; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D000199:Actins; D037322:Thyrotropin, beta Subunit; D014284:Triiodothyronine; D013972:Thyrotropin